Field Marks:A large fairly stout grey shark with a long pointed snout, small eyes, narrow, mostly erect- and narrow-cusped serrated upper anterolateral teeth without cusplets, long gill slits, lower teeth with narrow, usually serrated cusps, usually 15/14 to 15 rows of anterolateral teeth, no interdorsal ridge, moderately large pectoral fins, a large first dorsal with a short rear tip and a moderately large second dorsal with a short rear tip, and usually black tips on most fins in juveniles to adults.

Diagnostic Features:A fairly stocky species (up to about 2.6 m). Snout moderately long and moderately pointed; internarial width 1.3 to 1.7 times in preorallength; eyes circular and moderately large, their length 1.2 to 2.2% of total length; anteriornasal flaps low, triangular, and not elongated; upper labial furrows short and inconspicuous; hyomandibular line of pores just behind mouth corners not conspicuously enlarged: oill slits long, the third 3.8 to 4.9% of total length but less than half of first dorsalbase; usually 15/14 to 15 rows of anteroposteriorteeth in each jaw half but varying from 14 to 16/13 to 16; upper teeth with narrow, strongly serrated, erect to slightly oblique high cusps, and crown feet with slightly coarser serrations but no cusplets; lower teeth with erect, narrow, serrated high cusps and transverse roots. No interdorsal ridge. First dorsal fin large and falcate, with a pointed or narrowly rounded apex and posterior margin curving ventrally from finapex; origin of first dorsal fin usually over or slightly posterior to pectoralinsertion, but exceptionally near the pectoral free rear tip; inner margin of first dorsal short, about a third of dorsalbase; second dorsal fin large and high, its height 2.5 to 3.6% of total length, its inner margin short and 1.1 to 1.6 times its height; origin of second dorsal over or slightly anterior to anal origin; pectoral fins moderately large, falcate, with narrowly rounded or pointed apices, length of anterior margins about 18 to 20% of total length in individuals above 1 m long; 174 to 203 total vertebral centra, 88 to 102 precaudal centra. Colour grey or grey-brown above, white below; black tips usually present on pectorals, second dorsal, and ventralcaudallobe, and sometimes on pelvic and anal fins (anal usually plain), and black edges usually present on first dorsalapex and dorsalcaudallobe; adults in some areas may have plain or virtually plain fins. A conspicuous white band on flanks.

Habitatand Biology:A common tropical and warm-temperate, inshore and offshorepelagic shark, found on or adjacent to the continental and insular shelves but not truely oceanic. Commonly occurs close inshore, off river mouths and in estuaries, in shallow muddy bays, in the more saline parts of mangrove swamps, in island lagoons and along dropoffs on coral reefs as well as far offshore; rarely found deeper than 30 m. It can tolerate reduced salinities in estuaries and off river mouths, but does not penetrate far into fresh water.

Off Natal, South Africa, there is evidence of segregation of the local population. Sharks resident there consist mostly of adult males and non-pregnant females, with the addition of few young and adolescent individuals and periodic influxes of pregnant females during the spring; pregnant females mostly do not pup there but apparently migrate elsewhere, possibly to southern Mozambique where nursery grounds may occur. Off Florida these sharks are seasonally migratory and are absent during winter months.

This is a very active, fast-swimming shark that often occurs in large schools at the surface. It leaps out of the water, and like the related spinner shark (C. brevipinna), may rotate up to three times around its axis before dropping back into the sea. It is a less common spinner and leaper than its relative, however. This leapingspinning behaviour is thought to be used by the sharks while feeding on small schooling fishes; the sharks launch themselves vertically through the schools, spinning and snapping in all directions, and then breach the surface after their feeding run.

Viviparous, with a yolk-sac placenta; number of young 1 to 10 per litter, commonly 4 to 7. The gestation period is 10 to 12 months, with young being born in late spring or early summer off South Africa, Madagascar, India and in the North Atlantic (April to June) and mating and early growth of embryos occurring soon after this. Pregnant females move inshore to drop their young in nursery and pupping grounds. Maturity in South African waters occurs at an age of four years and a length of about 180 cm, with a maximum age of at least 12 years. Females are thought to produce young only in alternate years.

Primarily a fish-eater, with some cephalopods and crustaceans taken. Food includes a wide variety of bony fishes, including sardines, menhaden, herring and other clupeids, anchovies, ten-pounders (Elopidae), sea catfish, coronetfish, tongue-soles, threadfins, mullet, spanish mackeral, jacks, groupers, snook, porgies, mojarras, emperors (Lethrinidae), grunts, slipjaws, butterfish, croakers, soles, tilapia, triggerfish, boxfish and porcupine fish, as well as small sharks such as smooth-hounds (Mustelus), sharpnose sharks (Rhizoprionodon), the young of larger sharks (including dusky sharks), guitarfish, skates, butterfly rays, stingrays, eagle rays, squid, cuttlefish, octopi, crabs and lobsters. The high activity of this shark (aided perhaps by its relatively long gill slits) and its social behaviour makes it subject to feeding frenzies when a highly concentrated food source, like the fish byeatch of a shrimp trawler being dumped overboard, is competed for by numbers of these sharks.

Very few attacks on people have been attributed to this species, and it is likely that without a food stimulus or other special circumstances (like feeding stimuli provided by people that dangle their limbs in the water) that this species is of little hazard to people. Small individuals of this shark have approached divers, apparently out of 'curiosity', but circled them at a distance without closing, and appeared far more timid than Galapagos sharks (C. galapagensis) or silvertips (C. albimarginatus), which dominated them in contests for food. However, the blacktip commonly appears around spearfishing divers and has harassed them; and can get very aggressive and actively belligerant when contending a speared catch with a diver. Hence it should be treated with respect in baited circumstances, as with many other large sharks. Its speed may make the blacktip a difficult opponent when it becomes aggressive, particularly when several sharks are about and they become hyperstimulated.

Commonly taken by anglers trolling bait or stillfishing offshore in Florida and South African tropical waters. It may give an active, fast, spirited fight and even leap out of the water when hooked, like a low-powered mako, but sometimes is more dogged and loglike in its struggle. It is not recognized as a game fish by the International Game Fish Association.

Springer, S., 1963. Field observations on large sharks of the Florida-Caribbean region. In Sharks and survival, edited by P.W. Gilbert, J.A.F. Garrick and L.P. Schultz. Boston, C. Heath and Co., pp.93-113